Not a hope Ireland will leave - Ireland is currently the most positive country about the EU in the EU, not eurosceptic at all.
Also EFTA will be politically impossible after a leave vote. There is no politician on earth that could sell any deal with freedom of movement to the public in the event of leaving.
Nate
There are still deeply held eurosceptic views, and a brexit would bring them right back to the fore. Many business leavers over there are suggesting that Ireland should leave if the UK does for instance.
EFTA would be impossible as a permanent solution, but not as a stepping stone. We can join it hassle free, and then set a deadline for ending negotiations with Brussels to suit us.